syscall.go RawHistoryFolder

1// SPDX-License-Identifier: Apache-2.0
2// SPDX-FileCopyrightText: 2022 The Ebitengine Authors
3
4//go:build darwin || freebsd || linux || windows
5
6package purego
7
8const (
9	maxArgs     = 9
10	numOfFloats = 8 // arm64 and amd64 both have 8 float registers
11)
12
13// SyscallN takes fn, a C function pointer and a list of arguments as uintptr.
14// There is an internal maximum number of arguments that SyscallN can take. It panics
15// when the maximum is exceeded. It returns the result and the libc error code if there is one.
16//
17// NOTE: SyscallN does not properly call functions that have both integer and float parameters.
18// See discussion comment https://github.com/ebiten/purego/pull/1#issuecomment-1128057607
19// for an explanation of why that is.
20//
21// On amd64, if there are more than 8 floats the 9th and so on will be placed incorrectly on the
22// stack.
23//
24// The pragma go:nosplit is not needed at this function declaration because it uses go:uintptrescapes
25// which forces all the objects that the uintptrs point to onto the heap where a stack split won't affect
26// their memory location.
27//
28//go:uintptrescapes
29func SyscallN(fn uintptr, args ...uintptr) (r1, r2, err uintptr) {
30	if fn == 0 {
31		panic("purego: fn is nil")
32	}
33	if len(args) > maxArgs {
34		panic("purego: too many arguments to SyscallN")
35	}
36	// add padding so there is no out-of-bounds slicing
37	var tmp [maxArgs]uintptr
38	copy(tmp[:], args)
39	return syscall_syscall9X(fn, tmp[0], tmp[1], tmp[2], tmp[3], tmp[4], tmp[5], tmp[6], tmp[7], tmp[8])
40}